After owning an Asteroids Deluxe machine for a short time, you realize the beauty of the controls. Real leaf switches are really needed for the fast shooting, and are far less fatiguing than using microswitches. Also, using a joysitck will be too sloppy and slow for turning the ship... due to the long travel from one side to the other... and back again. If you miss a UFO or small asteroid by a hair.. and have to adjust a tiny touch in the other direction "Quickly", your going to have an issue with a Joystick response time.
That said... you need about a 1ft diameter circle of clear space to operate a trackball as it was intended to be used. In your picture, you would smash your hands into the 2nd players joystick. As you roll the trackball, your hand starts to come up at an arc.. so controllers that are low, like buttons, should be fine to place in front of the trackball (Nearest the monitor). However, even then, it should be a few inches past the trackball... to make sure there is enough space for the arc to happen.
(Although, if these buttons were not HOT buttons such as Escape.. a few glides over them should be ok. Its more about safety of your hands from being injured in that case)
If you place controls too deep into the Control panel, it will become fatiguing to have to reach that far up for extended periods of time.
Also, Imagine where your arms are going to be. Peoples forearms tend to angle out towards the bodies sides, with the elbow outwards. You need to make sure that each players arms are not going to be in each others way. As well as thinking about IF you can reach another controller thats slightly deeper... without any other controllers in the way of your forearm.
And... you may also consider, that it may too be uncomfortable, to rest your arms on top of other buttons and controllers.. to play the deeper controls.
You could make the control panel able to be lifted out, and spun around... so that the monitor side controls, were now player side controls.
You could make a trackball add-on, that you place over a button area... (feet high enough that there is clearance underneath)
You could make the asteroids panel on the front of the machine, that flips up and locks in place.
(Folding-Table like Locking mechanism)
You could make the asteroids panel a Pull-out and snap-locking drawer, thats located under the main CP.
You could make a dual trackball panel that has metal rails under it, that slides into locking holes in the machines front.
(make sure its hardened tube, or bar stock... something thats not going to bend from heavy pressure)
edit - Ohh, and buttons with a large arc like that... you will probably end up losing place of which buttons your fingers are resting on... because when you are not looking at them, and slide or raise off of them... you wont know exactly where they are inside of your mind. You often will end up landing on a button edge, instead of its center. Unless you are using Japanese flat top or convex buttons.. which I find do not feel good at all compared to the convex standard (for most of the arcade years). Just think about your Keyboard keys. They are all in a straight line. Its a common mistake people made.. and one that a lot of people end up regretting... (including myself).
Edit 2 : And your trackball is Still REALLY close to that 2nd player joystick.. which is a danger to peoples hands/fingers. It would be FAR better to offset the trackball closer to the player one sides buttons.. because they are lower, and pose no threat of broken fingers. Sure, it wound be symmetrical... but who cares. Not everything in this earth is symmetrical. Your cars controls are not... IMO, better to be safe than sorry... over something trivial as a certain look.